Generation of power using trichlorobenzene in a rankine-cycle engine

ABSTRACT

1,2,4-Trichlorobenzene is an inexpensive and useful working fluid for use in Rankine-cycle engines. Thermal stability at high temperatures is enhanced by constructing the engine, particularly the boiler, with ferritic alloy steels.

O United States Patent 11 1 1111 3,802,185 Tullock Apr. 9, 1974 [5 1 GENERATION OF POWER USING 3,553,142 1/1971 Figiel et a]. 252/67 TRICHLOROBENZENE IN A 3,702,534 11/1972 Bechtold 60/36 RANKINE CYCLE ENGINE 3,707,843 1/1973 Conner et al. .1 252/67 [75] Inventor: Charles W. Tullock, Landenberg, FOREIGN PATENTS OR APPLICATIONS 21,127 9/1912 Great Britain 60/36 [73] Assignee: E.I. du Pont de Nemours and OTHER PUBLICATIONS Company, Wilmington, Del, The Condensed Chemical Dictionary, 6th Edition, (page 1160) Copyright 1961, 5th Printing 1965 by [22] Filed. June 14, 1972 Reinhold Pub Corp [21] Appl. No.: 262,490

Primary Examiner-Edgar W. Geoghegan U S C] 60/649 252/67 Assistant Examiner-H. Burks, Sr.

[51] Int. Cl. F0lk 25/00 58 Field of Search 60/36; 252/67 [57] ABSTRACT 1,2,4-Trichlorobenzene is an inexpensive and useful [56] References Cited working fluid for use in Rankine-cycle engines. Ther- UNITED STATES PATENTS mal stability at high temperatures is enhanced by con- 3 040 528 6,1962 T b t I 60/36 structing the engine, particularly the boiler, with fera or e a. I 3,234,734 2/1966 Buss et al 1 60/36 alloy Steels 3,516,248 6/1970 McEwen 252/67 1 Claim, 2 Drawing Figures PUMP PATENTEDAPR 9mm v 3302.185

BOILER TURBINE REGENERATOR PUMP F I G: 2-

- F I G- 1 T EM PERATURE, F

ENTROPY, Bfu./|b

GENERATION OF IOWER'USING TRICHLOROBENZENE IN A RANKINE-CYCLE ENGINE FIELD OF THE INVENTION This invention relates to the use of a novel power fluid in Rankine-cycle engines.

BACKGROUND OF THE INVENTION External combustion engines offer a number of advantages over internal combustion engines such as a broader selection of fuel sources. Such engines are generally more readily adapted to low pollution operation in part due to the choice of fuel and .in part to the choice of combustion conditions which can be employed. The greater number of engines operating on the Rankine-cycle at the present time are conventional steam engines including piston engines and turbines. Screw expanders have also been proposed. While water is an inexpensive readily available power fluid, it is not without disadvantages such as expansion upon freezing. Also, because of the nature of the temperature-entropy diagram, it is generally necessary to usesuper-heated steam at high pressure and temperature in order to obtain acceptable efficiency and to avoid. wet vapor upon expansion. Further, when turbines are employed it is necessary to employ multiple stages. For these reasons, steam engines operating on the Rankin cycle are generally large stationary engines such as those employed for the production of electric power.

The present invention is, therefore, directed to providing a novel fluid useful in Rankine-cycle engines and particularly in small portable engines witheffieient aircooled condensers.

SUMMARY OF THE INVENTION The present invention can be defined as a method of generating power in which a working substance is heated and vaporized, does work in a prime mover, and after doing said work is condensed and recycled, wherein said working substance consists essentiallyof 1 ,2,4-trichlorobenzene.

THE DRAWINGS AND DETAILED DESCRIPTION OF THEINVENTION optimize the efficiench FIG. 2 is a temperature-entropy diagram for 1,2,4- trichlorobenzene.

Turning now to FIG. 1, the working substance is evaporated in the boiler 1'. This boiler can be any conventional form of boiler. Boilers of the rotating type wherein the liquid is distributed over alarge surface by centrifugal force are particularly efficient thermally and'produce high quality vapor. Such boilers are preferred for use with the working substances of the present invention. The vapor then passes to a prime mover such as a turbine 2 when it expands in the turbine nozzles and is employed to run an impulse turbine. The vapor can then be passedto a condenser 3 when it is condensed back to the boiler l by pump 4 and thus recycled. With the liquids of the present invention, small air-cooled condensers of high efficiency can be em- I relative to the liquid at the condenser temperature and ployed. It is, therefore, desirable to employ a condenser of smaller diameter attached to and rotating with the boiler. The liquid can then by pumped from the condenser to the boiler by centrifugal force.

Expansion of the vapor in the prime mover is essentially isentropic. The vapor of the working substance of this invention becomes superheated upon expansion. The efficiency of the cycle can, therefore, be improved by passing the exhaustfrom the turbine employed as a prime mover through a regenerator 5 wherein the excess heat is removed from the vapor and transferred to the boiler feed as taught by US. Pat. No. 3,040,528.

there is shown the temperature-entropy diagram for l,2 ,4-trichlorobenzene, the wohkingfluid of the present invention. Power is generated by the expansion of the trichlorobenzene from vapor at a pressure of 148.7 p.s.i.a. and temperature 655 F, point 11 on the diagram, in a turbine. Expansion is essentially isen-, tropic and the working fluid, therefore, is cooled following the line from 11 to 12 to a temperature of 459 F at the condensing pressure of 3.02 p.s.i.a. The vapor is cooled from 459 F to 312 F, preferably in a re'generatorbut optionally in the condenser to point 13 on the diagram. The vapor is then condensed to liquid at 312 F and 3.02 p.s.i.a. following the path 13 to 14 in the figure. The liquid at point '14 is pumped to1'48.7

p.s.i.a. and heated by the boiler, and also by regeneration, if that is employed, to point 15 and thereafter evaporated to vapor at 655 F and 148.7 p.s.i.a. to point 11 thereby completing the cycle.

For the above cycle, the following enthalpy values pressure have been calculated.

Point Pressure Temperature Enthalpy /p.s.i.a. Fl Btu/lb. 11 148.7 655 186.076 12 3.02 459 145.603 13 3.02 312 111.841 14 3.02 312 O '15 148.7 655 108.427

Without regeneration, this Rankine cycle thermal efflciency is about 22 percent. For percent regenera- THERMAL STABILITY DURING ENGINE- OPERATION:

This is necessary to permit prolonged operation in a closed system. In particular, any decomposition generating noncondensible gases would blanket and inactivate the condenser or require a constant purging device. Further, decomposition of the working fluid should not produce inslulating solid deposits in valves, nozzles, seals or on heat exchanging surfaces.

LOW TOXICITY:

The working fluids are preferably such that inhalation of vapors from accidental breakage of spills should not be damaging to health.

LOW FLAMMABILITY:

Theflammability of the fluids should be as low as possible to minimize the risks of fire.

LOW CORROSIVITY:

The liquids should not attack metals employed for engine construction.

HIGH MOLECULAR WEIGHT:

High molecular weight is particularly beneficial in the construction of low horsepower (i.e., l000 h.p.) turbine engines, since it permits operation with a single stage turbine at reasonable speeds. For this purpose the molecular weight should be at least 150.

HIGH LIQUID DENSITY:

As mentioned above, rotary boilers in which the working substance is maintained in the liquid state on an extended cylindrical surface by centrifugal force are particuarly useful for small Rankine-cycle engines. Rotary condensers which have a smaller diameter than the boiler and rotate therewith can be employed with advantage, and the centrifugal force employed to pump the liquid (optionally through-a regenerator) from the condenser to the boiler. The greater the liquid density of the working substance, the smaller the diameter of the boilder (and consequently of the small engine) which is required at a given speed of rotation .or conversely, for a given size' of boiler and condenser the slower the rate of rotation required to achieve efficient operation. The construction of a particularly preferred system employing a rotating boiler and condener is taught in the copending commonly assigned patent applications of William A. Doerner, U.S. Ser. No. 1 10,748 filed Jan. 28, 1971 as a continuation-in-part of U.S. Ser. No. 24,857 filed Apr. 6, 1970 and now abandoned U.S. Ser. No. 231,232 filed Feb. 3, 1972 and U.S. Ser. NO. 227,902 filed Feb. 22, 1972; also U.S. Pat. No. 3,590,786 and U.S. Pat. No 3,613,368 to William A. Doerner.

LOW FREEZING POINT:

cient air-cooled condenser. The thermal stahilityis surprisingly good in contrast tothe 1,2,3-isomer which is u d i mi tu e w 2 rish atqlzsszqnsms l:

mercial trichlorobenzene. Accordingly, commercial trichlorobenzene sould be purified to removed the 1,2,3-trichlorobenzene which can be achieved by known rnetho ds, e.g., by partial freezing of the commercial trichlorobenzene, followed by isolation of the liquid, unfrozen material which is enriched in the 1,2,4-isomer. In particular, 1,2,4-trichlorobenzene is especially stable in ferritic steels such as 1018 steel. The stability is less in alloy steel such as stainless steel which appears to catalyze decomposition of the trichlorobenzene. The melting point of 1,2,4-trichlorobenzene, 17C (63F), is the lowest of the three possible trichlorobenzene isomers.

The high molecular weight 1 81.4) renders trichlorobenzene particularly useful in small, single stage turbines operating at relatively low speeds. 1,2,4- Trichlorobenzene has a relatively low toxicity as determined by tests with rats. The Toxic Substances Annual List 1971, Herbert E Christensen. National Institute for Occupational Safety and Health, U.S. Department of Health, Educationand Welfare gives a value of LD 756 mg/kg rat for toxicity by ingestation.

The acute inhalation toxicity measured with room temperature air saturated with 1,2,4-trichlorobenzene vfiairti'spp'm) showed no deaths in 6 rats exposed for four hours. During the exposure lachrymation, salivation, pink ears, labored breathing and discoordination were observed. The body weight after exposure dropped to 84 percent of the initial weight the first day after exposure followed by normal weight gain for two weeks. l ,2 ,4-Tr ichlorobenzene is a mild skin irritant but does not, however, sensitize guinea pigs.

t rssp t fl mmab ity! flrtriahlvwwnz has a flash point of about 230 F. However, although a swab of glass wool impregnated with 1,2,4- trichlorobenzene is ignited in a flame, the ignited material extinguishcs itself'upon removal from the flame.

Finally. 1,2,4-trichlorobenzene can be obtained in large quantities at relatively low cost.

Since obvious modifications and equivalents in the invention will be evident to those skilled in the arts, I propose to be bound solely by the appended 'claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. The method of generating power by heating and vaporizing a working substance to a vapor in a ferritic steel container, expanding said vapor in a prime mover to do work, and after doing said work condensing said vapor and recycling said working substance, wherein said working substance consists essentially of 1,2,4- trichlorobenzene. 

